pH = measures acid-base

PaCO2 = partial pressure of CO2 in the blood, affected by CO2 removal in the lungs

HCO3 = measure the bicarbonate content of the blood; affected by renal production of bicarbonate

Normal ABG Ranges

• pH = 7.35 - 7.45
  • pH < 7.35 = acidosis
  • pH > 7.45 = alkalosis

• PaCO2 = 35 - 45
  • PaCO2 < 35 = alkalosis
  • PaCO2 > 45 = acidosis

• HCO3 =22 - 26
  • HCO3 < 22 = acidosis
  • HCO3 > 26 = alkalosis

• PaO2 =80 - 100

• CNS:
  • depressed acitivty, lethargy, confusion, stupor, coma
• Neuromuscular:
  • hyporeflexia, skeletal muscle weakness, flaccid paralysis
• Cardio:
  • delayed electrical conduction
  • bradycardia to heart block
  • Hypotension, thready peripheral pulses
• Respiratory:
  • Kussmaul respirations
    
• Skin:
• warm, flushed, dry skin (metabolic acidosis)
• pale - cyanotic, dry skin (respiratory acidosis)
  

Causes of Respiratory Acidosis

pH ↓ & PaCO2 ↑

HCO3 normal

anesthesia

drug overdose

COPD

pneumonia

head & neck trauma

muscle weakness

airway obstruction

electrolyte imbalance

inadequate chest expansion

Signs & Symptoms of Respiratory Acidosis

pH ↓ & PaCO2 ↑

HCO3 normal

hypoventilation → hypoxia

rapid, shallow respirations

↓ BP w/ vasodilation

dyspnea

headache

hyperkalemia

Dysrhythmias (↑ K+)

drowsiness / dizziness / disorientation

muscle weakness

hyperreflexia

Treatment of Respiratory Acidosis

pH ↓ & PaCO2 ↑

HCO3 normal

maintain patent airway

enhance gas exchange

oxygen therapy

bronchodilators

Causes of Metabolic Acidosis

pH ↓ & HCO3 ↓

PaCO2 normal

diarrhea - loss of HCO3

DKA

renal failure

shock

hypermetabolism

Signs & Symptoms of Metabolic Acidosis

pH ↓ & HCO3 ↓

PaCO2 normal

headache

decreased BP

hyperkalemia

muscle twitching

warm, flushed skin

nausea / vomiting / diarrhea

Changes in LOC: confusion, increased drowsiness

Kussmaul respirations

Treatment of Metabolic Acidosis

pH ↓ & HCO3 ↓

PaCO2 normal

Diarrhea = IV fluids, anti-diarrheals

DKA = insulin & IV fluids

Renal failure = dialysis

Causes for Respiratory Alkalosis

pH ↑ & PaCO2 ↓

HCO3 normal

Too much CO2 being exreted by the lungs

Hyperventilation

Fear

Anxiety

mechanical ventilation

Hypoxemia

high altitudes

shock

Signs & Symptoms of Respiratory Alkalosis

pH ↑ & PaCO2 ↓

HCO3 normal

seizures

Kussamaul respirations

hyperventilation

tachycardia

low or Normal BP

hypokalemia

numbness/ tingling of extremeties

lethargy & confusion

light headedness

nausea / vomiting

Causes of Metabolic Alkalosis

pH ↑ & HCO3 ↑

PaCO2 normal

Loss of acid

increase in HCO3

severe vomiting

excessive NG drainage / GI suctioning

thiazide diuretics

excessive use fo antacids

excessive Na+HCO3

Parenteral base administration: blood transfusions, TPN

Hyperaldosteronism

Signs & Symptoms of Metabolic Alkalosis

pH ↑ & HCO3 ↑

PaCO2 normal

nausea / vomiting/ diarrhea

tremors / muscle cramps

tingling of fingers & toes

hypokalemia

restlessness then lethargy

dyrhythmia - tachycardia

compensatory hypoventilation

confusion / decreased LOC / dizzy / irritable

• CNS:
  • increased acitivty
  • anxiety & irritability
  • tetany
  • seizures
  • Positive Chvostek's sign &  Trousseau's sign
  • paresthesia
• Neuromuscular:
  • hyperreflexia
  • muscle cramping & twitching
  • skeletal muscle weakness
• Cardio:
  • increased HR
  • normal or low BP
  • Respiratory:
  • increased rate & depth w/ respiratory alkalosis
  • decreased effort w/ metabolic alkalosis

Partial Compensation

• If you're seeing a pH outside the normal range, your disorder is either uncompensated or partially compensated.
  

• Partial compensation prevents the acid-base imbalance from becoming severe or life threatening

• Respiratory compensation occurs through the lungs, usually to correct for acid-base imbalances from metabolic problems.

• Renal compensation results when a healthy kidney works to correct changes in the blood pH that occur when the respiratory system is overwhelmed or not healthy

• Renal compensatory mechanisms are much more powerful than respiratory but are not as rapid

• Renal compensation are not fully triggered unless the acid-base imbalance continues for several hours to several days

What is it??

• Partially compensated respiratory acidosis
  • pH & PaCO2 match – respiratory
  • HCO3 odd one out
  • pH is not normal so only partially compensated

What is it???

ANSWER:

• Partially compensated metabolic alkalosis
  • pH & HCO3 match – metabolic
  • PaCO2 odd one out
  • pH is not normal so only partially compensated

What is it??

ANSWER:

• Fully compensated metabolic alkalosis
  • Even though pH is normal it s high normal which would be alkalosis
  • If pH were alkalosis then HCO3 would match – metabolic
  • pH is normal so fully compensated

What is it??

ANSWER:

• Fully compensated respiratory acidosis
  • Even though pH is normal its low normal which would be acidosis
  • If pH were acidosis then PaCO2 would match – respiratory
  • pH is normal so fully compensated